Actuation generally refers to a mechanism by which an object, or portion of an object, can be adjusted or moved by converting energy (e.g., electric energy, chemical energy, etc.) into mechanical energy. Actuators may be categorized by the manner in which energy is converted. For example, electrostatic actuators convert electrostatic forces into mechanical forces.
Piezoelectric actuation provides high bandwidth and actuation authority but low strain (much less than 1% typically), and requires high actuation voltages. Shape memory alloys (SMAs), magnetostrictors, and the newly developed ferromagnetic shape-memory alloys (FSMAs) are capable of larger strain but produce slower responses, limiting their applicability. Actuation mechanisms that are based on field-induced domain motion (piezos, FSMAs) also tend to have low blocked stress. The above actuation methods are based on the use of active materials of high density (lead-based oxides, metal alloys), which negatively impacts weight-based figures of merit. Thus, there is a need for a technology capable of providing high actuation energy density, high actuation authority (stress), large free strain, and useful bandwidth.
Certain methods of actuation using electrochemistry have previously been described, wherein the load-bearing actuation materials are in gaseous or liquid phase and may be expected to have low elastic modulus and consequently low actuation energy density and actuation stress, compared to the approach of the present invention. Despite the observation of displacement, mechanical work has not been demonstrated.
Accordingly, improved methods and devices are needed.